By Dr Trywell Muzerengi

Blood marks on an eggshell usually point to irritation or a minor injury to the hen’s vent, also called the cloaca, during egg laying. The condition is often short-lived, but understanding the causes helps farmers protect flock health and reduce losses.

Why it happens:

1. Oversized eggs – A larger-than-normal egg can stretch the vent, causing slight tearing and bleeding as it passes.
2. New layers – Pullets that have just started laying often have immature reproductive systems. Minor bleeding is common as the system adjusts.
3. Vent pecking – Aggressive pecking by other birds can damage the vent area. Small wounds then leave blood traces on the egg.
4. Parasites or infections – Internal worms or bacterial infections can inflame the vent, making bleeding more likely during laying.
5. Calcium shortage – Low calcium weakens eggshell formation and makes eggs harder to expel, increasing strain and injury risk.

What farmers can do:
Provide reliable calcium sources such as oyster shell or limestone grit to strengthen shells and ease laying. Reduce stress by avoiding overcrowding and sudden changes in the coop. Inspect hens regularly for vent wounds and isolate any bird showing irritation until it heals. Keep the coop clean and follow a consistent deworming schedule. If blood marks continue over several days, monitor the affected hen closely and seek veterinary advice.

Occasional blood spots are usually not a serious threat, but repeated bleeding may signal an underlying health issue that needs attention.

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